[tex]x^2+(\sqrt7-1)^2=(\sqrt7+1)^2\\\\x^2+7-2\sqrt7+1=7+2\sqrt7+1\\\\x^2=7+2\sqrt7+1-7+2\sqrt7-1\\\\x^2=4\sqrt7\\\\x^2=\sqrt{4\sqrt7}\\\\x=2\sqrt[4]{7}[/tex]
